Another Cedar Rapids main break leads to fish kills in urban trout steam

Chlorinated water from a main break leaked into McLoud Run trout stream in Cedar Rapids. (Photo courtesy of Iowa DNR)

Unofficial numbers from the Iowa Department of Natural Resources show about 1,250 fish were killed as the result of a water main break in Cedar Rapids that discharged chlorinated water into McLoud Run stream. 

The break occurred Monday morning and drained from 32nd Street into Iowa’s only urban trout stream. 

A dead white sucker found in McLoud Run trout stream. (Photo courtesy of Iowa DNR)

City officials worked to isolate the break and dispensed dechlorination tablets to the leaked  drinking water to minimize the impact on the stream. 

Chlorine is commonly used to disinfect municipal water. It’s safe for human consumption, but can be fatal to the sensitive fish species in the stream.

Andrea Errthum, a DNR environmental specialist who investigated the event, said the city responded very quickly to mitigate the break. 

“They were really on top of it,” Errthum said.

City water breakages have affected McLoud trout populations in the past. 

In January, a similar instance occurred, killing hundreds of trout in McLoud Run. Another break killed over a thousand trout in March 2023. 

Fisheries biologist Chris Mack said the fish most impacted by Monday’s spill were white suckers, a native fish species that tends to indicate water quality.  

A dead Brown Trout found in McLoud Run trout stream. (Photo courtesy of Iowa DNR)

The numbers from his count on Tuesday are not yet official, but Mack estimates only 30% of the killed fish were trout.

Mack said previous chlorinated water discharges have entered much further upstream and caused a greater area of impact. Monday’s incident only spread about a mile downstream, which helped to minimize the number of killed fish. 

“That was probably the saving grace,” Mack said. 

He thinks many of the trout were spared because the department stocks the catch-and-release stream with small fish high upstream. 

Mack said McLoud is “unique” and an important way to expose more people to trout fishing in the state. 

“It’s basically an opportunity for people in this part of the state to go trout fishing year round,” Mack said. “While it is a frequent issue, we still intend to maintain it as a trout stream.” 

DNR will release official numbers of fish kills and monetary impact by the end of the week.